The objective of the research in Phase I is to establish the feasibility of producing a small, lightweight, man-portable gas chromatograph-mass spectrometer (GCMS) that is capable of performing in situ analyses of unknown compounds of biomedical interest. The design of the proposed instrument is based upon a miniaturized GCMS developed for the NASA Mars Lander program. The rugged design, stability, and highly automated operation of this instrument are well suited to a portable, terrestrial GCMS instrument that can be used for biomedical investigations including field testing in emergency situations or under other circumstances where in situ analyses are either necessary or desired. In this Phase I research, the basic design, which is now in a breadboard configuration, will be adapted to the special requirements of biomedical testing. This will include incorporation of an electro-optical ion detector (EOID) for increased sensitivity and selected ion monitoring as well as flexible ionization (currently electron impact ionization is used), simplified sample introduction into the GCMS system, and computer-aided identification of mass spectra. (5)